Reconstituted tobacco composition

ABSTRACT

A reconstituted tobacco sheet is disclosed in which finally divided tobacco is combined with an adhesive consisting essentially of ethyl cellulose with an ethoxyl content of 45.5 percent to 46.8 percent and a viscosity at a 5 percent concentration of at least 5,000 cps at 25* C. The product produced is characterized by a substantial amount of wet strength and can be plasticized with conventional glycol humectants.

United States Patent Inventors Howard M. Halter Norwalk;

Otto K. Schmidt, Windsor, both 01, Conn. 872,792

Aug. 25, 1969 June 15, 1971 AMF Incorporated Division of Ser. No.688,663, Dec. 7, 1967. Pat. No. 3,500,333.

Appl. No. Filed Patented Assignee RECONSTITUTED TOBACCO COMPOSITION 4Claims, No Drawings U.S. Cl 131/17, 131/140 Int. Cl. A241) 03/14FieldofSearch 131/140R, 17

[56] References Cited UNlTED STATES PATENTS 3,288,148 11/1966 Detertetal131/140 3,322,130 5/1967 Panzer et a1. 131/17 3,416,537 12/1968 Townend131/140R Primary Examiner-Melvin D. Rein; Attorneys-George W. Price andMurray Schaffer RECONSTITUTED TOBACCO COMPOSITION This is a DivisionalApplication of Ser. No. 688,663, filed Dec. 7, 1967, now U.S. Pat. No.3,500,833.

This invention relates to the preparation of reconstituted tobaccoproducts characterized by resistance to degradation by moisture. Moreparticularly, it relates to tobacco products containing a particulargrade of water-insoluble adhesive material.

In recent years, tobacco manufacture from finely divided tobacco andadhesives has assumed substantial commercial importance. Products havebeen made which include sheets, shreds and other shaped articles. lngeneral, these products have either had a very substantial resistance todisintegration in the presence of moisture or else have had hardly anysuch resistance. Effectively, the water-soluble tobacco products havesuffered when exposed to the action of saliva and various treatmentsolutions used in the application of flavors and the like.

Two basic types of water-insoluble tobacco products are possible. Mostwater-insoluble products used commercially today are made fromcombinations of tobacco, water-soluble adhesives and insolubilizing orcrosslinking agents which react with or crosslink the hydrophilichydroxyl groups on the water-soluble adhesives to render the productswater insoluble. Some of these water-insoluble products, while generallysatisfactory, particularly when first manufactured, have tended undersome storage conditions to lose much of their water insolubility, Thisloss of water insolubility is related to hydrolysis of insolubilizingcrosslinks caused in some cases by instability of these linkages to highmoisture conditions, at which such products are frequently stored, or toammoniacal vapors created by continuing fermentation of the fillertobacco in smoking articles such as cigars. Virtually all of suchwetstrength tobacco products will lose at least a portion of their wetstrength at some combination of conditions involving moisture content,temperature, pH and time.

A second basic class of water-insoluble tobacco products achieves itsinsolubility through the use of water-insoluble, organic-solvent-solubleadhesives. Such products may be made from nonaqueous suspensions oftobacco particles in a viscous dispersion of the adhesive in a suitableorganic solvent. In principle, one would expect that such tobaccoproducts would enjoy a dominant position commercially, since they avoidthe problems of stability of wet strength associated with crosslinkedaqueous adhesive systems. However, such is not the case.

It has been found that water-insoluble adhesives which are sufficientlyhydrophobic to produce tobacco products with the requisite waterresistance result in distinctive, nontobacco, objectionable aromas oncombustion, which render the resultant products unacceptablecommercially. Water-insoluble, organic-solvent soluble adhesives in thiscategory include cellulosic derivatives with hydrophobic substituentssuch as ethyl or benzyl groups. The problem is increased by the factthat the hydrophobic adhesives generally require unusual plasticizers inorder to give the resultant tobacco sheet the elongation and pliabilityrequired for satisfactory performance on automatic machinery. Theseplasticizers, such as the polyester types used to plasticize tobaccosheets with hydrophobic adhesives described by Hotelling et al. in U.S.Pats. Nos. 2,984,244, 2,976,873 and 2,957,478, contribute nontobaccoobjectionable aromas on combustion. The combination of such plasticizerswith hydrophobic adhesives in tobacco products results in products whosecombustion aroma is unacceptable commercially. Accordingly, the onlytobacco products including water-insoluble adhesives which are incommercial use are cellulosic types with a substantial degree of methylsubstitution. Since the methyl group is decidely less hydrophobic thanthe ethyl group, highly substituted methylcellulose is compatible withconventional glycol humectants. However, the drawback of such adhesivesis that, although soluble, they are extremely water sensitive, and theyinvariably result in products with only minimal wet strength.

It is an object of this invention to provide tobacco productscharacterized by a substantial amount of wet strength.

It is a further objective of this invention to provide a wetstrengthtobacco product utilizing a particular grade of a hydrophobic adhesive.

It is another objective of this invention to provide tobacco productswith substantial amounts of wet strength made with a hydrophobicadhesive that can be plasticized with conventional glycol humectantsnormally employed in tobacco manufacture.

It is also an objective of this invention to provide wetstrength tobaccoproducts with commercially-acceptable taste and aroma propertiesincluding a particular grade of a hydrophobic adhesive.

Additional objectives will become apparent from the description of theinvention which follows.

While the invention will be described in connection with tobacco sheet,the adhesive of the present invention may likewise be advantageouslyused with tobacco in other shapes such as rods, cylinders, plugs shreds,and the like. Accordingly, it will be understood that the inventioncontemplates also tobacco manufacture of this kind.

Ethylcellulose, a water-insoluble hydrophobic adhesive, has beenconsidered as a potentially useful adhesive for reconstituted tobaccoproducts for many years. It is mentioned in this regard in severalpatents, including U.S. Pats. Nos. 2,957,478, 3,062,688 and 2,797,689.Frankenburg, in U.S. Pat. 2,797,689, recognized that the combustionaroma of ethylcellulose and other hydrophobic adhesives was unacceptablein tobacco products, and attempted to overcome this problem through theuse of siliceous catalysts. Detert et al. in U.S. Pat. No. 3,062,688,discloses a tobacco product employing highly methylated methylcelluloseas the adhesive, to which he adds sufficient ethylcellulose oracetylcellulose to provide some degree of water resistance. This is acompromise"-type product, since products containing highly methylatedmethylcellulose as adhesive are stated by Detert to be capable of takingup a very high content of pulverized tobacco which has a desirableeffect with respect to taste and burn, and also has desirable mechanicalproperties which allow it to be worked by machine or hand, but sufferbecause of a lack of wet strength. On the other hand, tobacco sheetsmade with hydrophobic adhesives such as acetylcellulose orethylcellulose had good wet strength, but would not take high tobaccoloadings and would not handle satisfactorily on machines or by hand. Itis obvious that by blending ethylcellulose with highly methylatedmethylcellulose that the resultant wet strength is less than would beobtained with ethylcellulose alone, and the tobacco loading, taste andburn and machine workability properties are poorer than would beobtained with highly methylated methylcellulose alone.

Hotelling et al. in U.S. Pats. Nos. 2,984,244, 2,976,873 and 2,957,478obtains good wet strength in his tobacco products by using medium ethoxy100 cps ethylcellulose as the sole adhesive, and also obtains goodmachine workability by his discovery that certain polyester types willplasticize tobacco sheets with ethylcellulose adhesives. However, it isstated in U.S. Pats. Nos. 2,957,478 and 2,984,244 that such products canonly be made at tobacco contents. up to percent, at which point thedecrease in tensile strength and elongation makes the product marginal.The ethylcellulose content, even in the product with 85 percent tobaccocontent, is still about 12 percent, and is even higher in the lowertobacco content products. This combination of high ethylcellulosecontent and the presence of polyester plasticizers, both materialshaving unusual, nontobaccolike burn aromas, results in products which wehave found to be unacceptable in commercial smokingarticles.

In the present invention, the disadvantages associated with the use ofethylcellulose as a tobacco adhesive in the prior art have been overcomethrough the use of a particular grade of ethylcellulose having anethoxyl content of 45.5-46.8 percent (degree of substitution of 2.28 to2.38 ethoxyl groups per anhydroglucose unit) and a viscosity of at least5,000 cps. The viscosity is for a 5 percent concentration ofethylcellulose by weight in 80.20 toluene: ethanol by weight at 25 C.,as measured with a Brookfield viscometer.

Use of this particular grade of ethylcellulose has several unusual andas yet unexplainable results. First, the tobacco loading which theethylcellulose can bind to produce tobacco products which still exhibitthe type of properties required for good machine workability isincreased two to six fold with this grade of ethylcellulose, allowingpreparation of tobacco products containing 27 percent ethylcellulose inplace of the 12-20 percent levels required previously. Second, use ofthis particular grade of ethylcellulose in tobacco formulations at the27 percent level unpredictably allows plasticization with standardglycol-type humectants to produce tobacco sheet products with 15-35percent wet elongation and with the requisite strength and pliabilityfor satisfactory workability on tobacco machinery. Accordingly, the needfor the polyester plasticizers described by Hotelling et al. iseliminated. Overall, the combination of low ethylcellulose content, hightobacco content, and the use of conventional glycol humectants, all madepossible by the use of this particular grade of ethylcellulose, resultsin wet-strength tobacco products which closely resemble natural tobaccoin taste and aroma and are accordingly of significant commercial value.

The properties of ethylcellulose are known to be dependent on the degreeof substitution (ethoxyl content) and on the molecular weight, which inmost cases can be measured by viscosity. The degree of substitution ofethylcellulose affects the softening point, hardness, water absorption,solubility in ethanol and solubility in 80.20 toluene: ethanol. On theother hand, there are certain other properties such as tensile strength,elongation and flexibility which are not greatly affected by the degreeof substitution, but which depend largely upon the degree ofpolymerization or molecular weight. For pure (unloaded) ethylcellulosefilms, the tensile strength and elongation increase as the molecularweight or viscosity increases. However, there is a marked leveling offof the curves for tensile strength and elongation versus viscosity gradebetween the 50 and 100 cps types. This means that very little additionaltensile strength or elongation can be gained by using higher viscositytypes than about 100 cps ethylcellulose. Such higher viscosity gradesare used for applications where increased viscosity is desirable, sinceimprovements in film properties do not result.

With a knowledge of the factors and relationships involved in theproperties ofpure ethylcellulose films as background, it was unexpectedto find that one particular grade of ethylcellulose, that with 45.5 to46.8 percent ethoxyl and at a 5 percent concentration a viscosity of atleast 5000 cps, results in a completely different effect when highlyloaded with ground tobacco. This grade of ethylcellulose, when loadedwith tobacco, results in films which have substantially greater tensilestrength than comparable formulations made with all other grades ofethylcellulose. Equally unexpected is the finding that tobacco-loadedfilms of this grade of ethylcellulose are readily plasticized withconventional glycol humectants for tobacco, such as triethylene glycol,propylene glycol or glycerine, to produce products with l5-35 percentwet elongation. When other grades of ethylcellulose are plasticized withsuch humectants in tobacco formulations, wet elongations of 10 percentor less invariably result.

Any of the solvents which dissolve ethylcellulose with a degree ofsubstitution of 45.5-46.8 percent ethoxyl may be employed in themanufacture of tobacco products according to thisinvention. Suchsolvents include methanol, ethanol, methylene chloride, toluene-ethanolmixtures and isopropanol-water mixtures containing from 88 percent to 97percent isopropanol. The best solvents for this grade of ethylcelluloseare 80:20 toluene; methanol or 80:20 toluene: ethanol (weight/weight),and use of either of these solvent mixtures results in tobacco productswith maximum tensile strength and elongation properties.

The procedure involved in the manufacture of tobacco products involvesdispersion of the ethylcellulose adhesive in the solvent forethylcellulose, followed by the addition of tobacco dust. The viscosityof the resultant dispersion should be at least sufficient to preventseparation or settling of the tobacco dust. Generally, a minimum of3,000 cps viscosity for the resultant dispersion, as measured by aBrookfield viscometer, is required to prevent separation. Otheradditives such as humectants or plasticizers, fibers, fungicides, ashadditives such as silicious earth or color additives may be incorporatedinto the tobacco suspension prior to shaping. If tobacco sheet is to beprepared, the resultant tobacco slurry may be cast or otherwise appliedto a moving belt at a thickness which, on drying, will result in thedesired tobacco film thickness. Depending on the solvent employed andits volatility, the shaped tobacco slurry may be air dried or dried atelevated temperatures, such as by steam-air mixtures or warm or hot airimpinging on the underside of the belt. The drying temperature should bekept below the boiling point of the solvent employed, or bubbling of thesolvent and disruption of the resultant film occur. For toluene:methanol /20, weight/weight) solvent systems, drying at temperatures ofabout 50 C. results in both good film properties and sufficiently rapiddrying rates. The organic solvents evaporated from the tobacco productsare recoverable by conventional processes and can be reused. The shapingof the resultant slurry may be made by any one of the well known methodsnow in use in the art. A suitable method and apparatus for the castingof the slurry into a sheet may, for example, be found in the followingU.S. Pats. Nos. to R. C. Osborne et al. 3,250,315 and 3,294,554 and inthe U.S. Pat. No. 3,145,716 issued to R. C. Gertz et al.

The following examples are provided as further illustrations of theinventive concept, and should not be construed as limitations on theinvention.

Example 1 A sample of ethylcellulose with an ethoxyl content of 46.8percent and at a 5 percent concentration a viscosity in 80/20toluene/ethanol of 5,400 cps at 25 C. was used in this example. TheBrookfield viscometer is used to measure viscosity. The first step inthe preparation of a tobacco slurry is the preparation of a 2 percentsolids dispersion of one part of this ethylcellulose in 80/20toluene/ethanol (weight/weight), with agitation being continued untildispersion is complete. To the resulting dispersion is added, withagitation, 0.2 parts triethylene glycol, 30 parts of tobacco ground tominus 80 mesh U.S. Standard sieve size, and sufficient additional 80/20toluene/ethanol solvent to produce a final total solids of 25 percent inthe tobacco slurry. The resultant uniform tobacco dispersion is cast ona moving stainless steel belt at a thickness such that the final driedfilm will weigh approximately 9 grams per square foot. The cast tobaccoslurry film is dried with warm (45 C.) water impinging on the undersideof the belt. The dried tobacco film is remoistened to 20 percentmoisture to facilitate doctoring from the belt. The resulting product isparticularly suitable for use as a cigarette or cigar filler, dependingon the particular type of tobacco employed. The product handles well onmachinery required for such applications, and, due to the lowethylcellulose content, has taste and aroma qualities comparable tonatural tobacco.

Example 2 A sample of ethylcellulose with an ethoxyl content of 45.5percent and at a 2 percent concentration a viscosity in 80/20toluene/ethanol of 10,000 cps at 25 C. was employed in this example. A1.2 percent solids dispersion of one part of this ethylcellulose in80/20 toluene/methanol (weight/weight) was prepared, using agitationsufficient to insure complete dispersion. To the resulting dispersionwas added 0.5 parts glycerine,

0.2 parts diatomaceous earth and 14 parts of Wisconsin tobacco ground tominus 120 mesh US. Standard sieve size. Agitation is continued until auniform dispersion is obtained. The resulting tobacco slurry is cast onan endless moving stainless steel belt at a thickness such that, afterdrying, a tobacco sheet weighing 3.03.5 grams/ft will be obtained. Thecast tobacco-slurry film is dried at 50 C. with a suitable steam-airmixture impinging on the underside of the belt. The dried tobaccocomposition is remoistened to 30 percent moisture content to facilitatedoctoring from the belt. The product was found to be particularlysuitable for use as a cigar wrapper, by virtue of its tensile strength,elongation and pliability. The average properties, as measured on aScott Tester after equilibration at 80 percent Relative Humidity and 72F. for 24 hours, were as follows: L-6* a 2 percent concentration wastaken since it was found that the material was too viscous at a 5percent concentration for accurate measurement in the Brookfieldviscometer.

Sheet Weight: Percent Moisture:

3.24 grams/ft 18.7 percent Tensile Strength, Equilibrated: 280grams/inch Tensile Strength, Wet: 200 grams/inch Elongation,Equilibrated: 17 percent Elongation, Wet: 32 percent The tobaccocomposition of this invention has many useful applications and smokingarticles such as cigars, cigarettes, pipe tobacco as well as chewingtobacco made in whole or in part from this material, are within thecontemplation of the invention. As sheet material it may be fed :fromrolls to automatic machines, for example, cigar machines, for use as abinder or wrapper. It may also be shredded for filler in pipes,cigarettes, and cigars. It may be mixed with shredded whole tobacco orused alone. It may serve as an outside wrapper for cigars or cigarettesand has the advantage of uniformity in appearance and in physicalproperties as well as uniformly blended flavor.

While the invention has been described in its preferred embodiment, itwill be understood that the invention is not limited to the specificdetails set out for purposes of illustration and that those skilled inthe art may make various changes in these details within the scope ofthe claims without departing from the spirit of the invention.

What we claim is:

l. A smoking composition comprising finely divided tobacco and adhesivetherefor consisting essentially of ethyl cellulose with an ethoxylcontent of 45.5 percent to 46.8 percent and a viscosity at a 5 percentconcentration of at least 5,000 cps at 25 C.

2. The composition of claim 1 in which said ethyl-cellulose adhesive hasa viscosity at a 2 percent concentration of not more than about 10,000cps at 25 C.

3. The composition of claim 1 in which said ethyl-cellulose adhesivecomprises 27 percent of the final smoking composition.

4. The composition of claim 1 comprising additionally a glycolhumpectant.

2. The composition of claim 1 in which said ethyl-cellulose adhesive hasa viscosity at a 2 percent concentration of not more than about 10,000cps at 25* C.
 3. The composition of claim 1 in which saidethyl-cellulose adhesive comprises 2-7 percent of the final smokingcomposition.
 4. The composition of claim 1 comprising additionally aglycol humpectant.